disappeared, leaving vacuoles with a narrow rim 

 of stainable material. The significance of dif- 

 ferent types of rods, some with granules, some 

 with vacuoles, and some with neither, is not 

 known. Are they nothing more than differences 

 between individuals or are they handles that can 

 jje used to gain an insight into the bird's condi- 

 tion of health and disease? 



Information is needed also on the chemical 

 nature of the rods and their granules. Whatever 

 may be the significance of the granules, they are 

 part of the apparently normal development and 

 may be found in heterophil myelocytes. Weid- 

 emeich ( 1911) according to Lundquist and Hed- 

 lung (1925) concluded that the uncolored spots 

 within the rods are merely optical phenomena. 

 Lundquist and Hedlung found central granules 

 in vital preparations but not in stained smears 

 and agreed with Weidenreich that the central 

 granules are not definite organelles. Burck- 

 hardt (1912) expressed essentially the same 

 ]>oint of view: ". . . In der Mitte der Spindel 

 wird oft ein ungefarliter Punkt sichtjjar. der je 

 nach der Stellung der Mikrometerschraube bald 

 aiifblitzt, bald Schwarz erscheint. Ueber die 

 Zusannnensetzung dieses Punktes wurde schon 

 mehrfach diskutiert, mir scheint er am einfach- 

 sten als Lichtbrechungsphanomen zu erklaren.'"' 

 Anyone studying avian blood soon recognizes 

 the fact that the rods show varying degrees of 

 dissolution. Figures 154—16.5 show a progres- 

 sive series from clearly tlefined and well-devel- 

 oped rods to no trace of rods, but the story does 

 not read in quite this sequence. The granules 

 are more resistant to the processes of dissolution 

 ihan are the rods. If the rods without granules 

 flisappear from figure 154 there is left a cell like 

 lliat shown in figure 165, but if a cell like that 

 shown in figure 1.55 loses its rods there remains 

 a ct'll like figure 164. Figure 1.56 would result 

 in sometliing like figure 163, and figure 157 

 would result in something like figui-e 161. In 

 each case of the loss of rod substance, the cell has 

 come to look more like an eosinophil; in some 

 instances the resemblance is quite close (fig. 

 161 ). However, there is no implication in what 



"Translation: In the middle of the spindle there can often 

 he seen an unstained dot. and after the adjustment of the 

 niierometric srrew this often sliows up as light, sometimes as 

 dark. Tliere has heen much discussion already over the com- 

 position of this dot: it seems to me simplest to explain it as 

 a phenomenon of light diffraction. 



has been said that heterophils become eosino- 

 phils. This similarity of appearance under some 

 conditions is probably the basis for more con- 

 fusion in making accurate differential counts 

 than any other single factor. 



How are such heterophils and eosinophils to 

 be distinguished? This will be discussed more 

 fully after the eosinophils have been described, 

 but the most important fact is that the rods as 

 they break down or go into solution give the cyto- 

 plasm an orange or pinkish color such as is read- 

 ily seen in figures 158-162. The background 

 color of the true eosinophil is practically always 

 light blue. That difference, coml)ined with the 

 fact that in most cases some part of the hetero- 

 phil nucleus is pale and poorly stained, makes it 

 relatively simple to distinguish the two granulo- 

 cytes. This characteristic difference in back- 

 ground color was observed in the heterophils and 

 eosinophils of reptiles by Ryerson (1943). 



Nuclear staining is extremely variable, as may 

 be seen in the series of figures 2, 1 and 154-167. 

 Sometimes the staining is vigorous as in figure 

 2, 1. where the nuclear lobes are clearly defined. 

 In other examples the nuclei vary in their recep- 

 tivity to stain from those moderately well stained 

 as in figures 156 and 167 to those in which there 

 is no trace of chromatin pattern or a distinct nu- 

 clear boundary. In the same cell (figs. 157 and 

 158) one lobe of the nucleus may be stained and 

 the more central ones may not be stained. Often 

 there will be a difference in staining of the same 

 lobe, the more central portion being faint and the 

 part adjacent to the cell wall fairly dark. Fail- 

 ure of the nucleus to stain is not a mark of de- 

 generation as indicated by Emmel (1936) but 

 merely means that Wright's stain failed to pene- 

 trate the cell and color the nucleus properly. 



The normality of the heterophil nucleus can be 

 ([uite easily and convincingly demonstrated if, 

 after the smear is made on the slide, the blood is 

 allowed to acquire a dull sheen and is then 

 dipped immediately into Petrunkevitch No. 

 2 (see ch. 7). If stained with May-Griinwald 

 Giemsa the nucleus appears as shown in figure 

 203. The treatment destroys the rods or distorts 

 litem so that they run together as a network but 

 reveals the nuclear structure in all its detail. 

 In none of these slides was there any indication 

 of nuclear degeneration. It is obvious that an 

 Arneth index could not be obtained from a dry 

 fixed Wright's or a May-Griinwald Giemsa 



83 



